| 单色光源的光学分辨率以半高全宽值(FWHM)来表征,它依赖于光栅刻槽密度(mm-1)及光学入瞳直径(光纤或狭缝)。配置您的系统时,必须平衡两个重要的因素:
1) 光栅刻槽密度增加,分辨率增大,但光谱范围及信号强度会减小。
2)
狭缝宽度或光纤直径变窄,分辨率增大,但信号强度会减小。
如何估算光学分辨率(nm,FWHM)
1. 1. 确定光栅光谱范围,找到光栅的光谱范围通过:
2. 2. 光栅光谱范围除以探测器像元数,结果为dispersion。
Dispersion (nm/pixel) = 光谱范围/像元数
下表列出了不同型号光谱仪的探测器像元数
|
光谱仪型号 |
探测器像元数 |
|
USB2000 Spectrometer |
2048 |
|
USB4000
Spectrometer |
3648 |
|
HR2000 Spectrometer |
2048 |
|
HR4000
Spectrometer |
3648 |
|
NIR256-2.1
Spectrometer |
256 |
|
NIR256-2.5 Spectrometer |
256 |
|
NIR512
Spectrometer |
512 |
|
NIR512-2.2
Spectrometer |
512 |
|
QE65000 Spectrometer |
1044 |
3.
确定像素分辨率
下表列出了不同狭缝(或光纤直径)尺寸下的像素分辨率。尽管狭缝入射宽度不同,但高度一致(1000um)。
|
光谱仪型号 |
5 um
狭缝
|
10 um
狭缝 |
25 um
狭缝 |
50 um
狭缝 |
100 um
狭缝 |
200 um
狭缝 |
|
USB2000 Spectrometer |
~3.0 pixels |
~3.2 pixels |
~4.2 pixels |
~6.5 pixels |
~12.0 pixels |
~24.0 pixels |
|
USB4000
Spectrometer |
~5.3 pixels |
~5.7 pixels |
~7.5 pixels |
~11.6 pixels |
~21.0 pixels |
~42.0 pixels |
|
HR2000 Spectrometer |
~1.5 pixels |
~2.0 pixels |
~2.5 pixels |
~4.2 pixels |
~8.0 pixels |
~15.3 pixels |
|
HR2000+ Spectrometer |
~1.5 pixels |
~2.0 pixels |
~2.5 pixels |
~4.2 pixels |
~8.0 pixels |
~15.3 pixels |
|
HR4000
Spectrometer |
~2.0
pixels |
~3.7
pixels |
~4.4
pixels |
~7.4
pixels |
~14.0
pixels |
~26.8
pixels |
NIRQuest
512 Optical Resolution |
N/A |
~2.0 pixels |
~3.1pixels |
~3.6 pixels |
~6.6 pixels |
~12.3 pixels |
NIRQuest
512-2.2 Optical Resolution |
N/A |
~1.3 pixels |
~2 pixels |
~2.3 pixels |
~4.2 pixels |
~7.9 pixels |
NIRQuest
256-2.1 Optical Resolution |
N/A |
~6.7 pixels |
~7.6 pixels |
~8.9 pixels |
~11.2 pixels |
~17.9 pixels |
NIRQuest
256-2.5 Optical Resolution |
N/A |
~8.3 pixels |
~9.5 pixels |
~11.1 pixels |
~13.9 pixels |
~22.2 pixels |
|
QE65000 Spectrometer |
~2.0 pixels |
~2.2 pixels |
~2.6 pixels |
~3.3 pixels |
~4.7 pixels |
~8.9 pixels |
4.
4. 计算光学分辨率(nm)
Dispersion (Step 2) x
Pixel Resolution
(Step 3)
Example: Determine the Optical Resolution of a USB4000 Spectrometer
with Grating #3, 10-micron Slit
举例:确定光学分辨率,光谱仪型号:USB4000,光栅型号:#3,狭缝宽度:10um
650nm(#3光栅光谱范围)/3648(USB4000探测器像元数)X5.6(像素分辨率)=0.18X5.6nm=1.0nm(FWHM)
注意: 结果值作了取整近似。
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